Brandon has a stellar amateur record of 230–35.In 2004 Ríos became the U.S. National Amateur Featherweight champion, he was also a United States Olympic alternate at 125 lbs.[3] "When I met Roberto in the Olympic trials in Mississippi, that’s when Roberto came and worked my corner, which it was a bad mistake," Rios said as García laughed. "I should have never done that because my dad was my amateur coach through my whole career. You get used to one person and then you come with another guy and he doesn’t really know you? To me, it kind of messed me up. But then again, I’m glad we met because we exchanged information and he brought me down here."[4]

He next fought in a WBA title eliminator against the undefeated contender Anthony Peterson, on a HBO Boxing After Dark card.[8] Rios dropped Peterson to the canvas with a left hand at the end of the fifth round.[9] In the sixth round, a desperate Peterson landed several low blows on Ríos, losing two points in the process.[10] In the seventh round, Peterson landed low blows once again, prompting the referee to stop the bout and award Ríos a disqualification victory.[11] Brandon was leading on all three scorecards before the stoppage.[8]

A much anticipated rematch was held on March 30, 2013 at the Mandalay Bay in Las Vegas, Nevada. Like the first fight, both came in with a lot of fireworks as they continued to go toe to toe, until Alvarado changed strategy and became a lot more evasive and hard to hit with fancy footwork. Alvarado defeated Rios by unanimous decision with scores of 115–113, 115–113 and 114–113. Top Rank promoter Bob Arum dismissed another rematch and suggested to let the two boxers face other fighters first.[19]

Rios and Pacquiao battled for the vacant WBO International Welterweight title on November 23, 2013, at The Venetian Macao resort & hotel in Macau of the Special administrative regions in China against Ring No. 4 ranked Welterweight, Ring No. 7 ranked pound for pound and former WBO Welterweight Champion Manny Pacquiao. Rios was guaranteed a purse of $3 million for this fight which is the highest of his boxing career. On August 5, Ríos and Pacquiao hit the road on a U.S. tour promoting the fight. Pacquiao won the 12 round match and the WBO International Welterweight title very easily.[20][21] After the fight, Ríos tested positive for methylhexaneamine.[22]

Brandon married Victoria López in August 2010 and has four children, two from a previous relationship.[24][25] Ríos gave the names Laila and Mia to his two daughters, after boxers Mia St. John and Laila Ali. His sons are named Marco Antonio, after Mexican World Champion Marco Antonio Barrera and Brandon Jr.[26]

As amateur boxers both Brandon Ríos and Victor Ortíz fought out of the same boxing gym in Oxnard, California, the Garden City Boxing Club where they were both trained by Manuel Rios.[27][28] For a short time Brandon's father trained Ortíz when they both still lived in Kansas. Ortíz would later move to Oxnard to train under Roberto García, Rios also left Kansas after being invited by García to train in Oxnard.[29] In 2009 after an incident involving Brandon, Victor Ortíz and Victor's younger brother, Temo Ortíz, their relationship became strained.[30] A fight between Ríos and Ortiz has been proposed at a catch weight of 138 lbs or even at 140 lbs, with Ríos stating on numerous occasions that he's gotten the better of Ortiz many times during sparring when they were growing up.[31]

In the much anticipated lead up to the fight at Cowboys Stadium, Ríos made headlines along with Antonio Margarito and Roberto García when Elie Seckbach interviewed the three of them and showed the group mocking Manny Pacquiao's trainer Freddie Roach, Roach has Parkinson's disease. Elie Seckbach made a video responds defending Rios and Margarito, and stated that the media misunderstood their jesters. Seckbach stated that they were actually making funny of Freddie Roach's comments where Roach said that Margarito was going to get knocked out. García explained that Ríos was "joking around", and that Brandon was also unaware that Roach is suffering from Parkinson's disease.[32] In the video, Ríos explains that it was a response to Freddie Roach's trash talking.